High-frequency electrical resonator



y mm N. L.. HARRIS ET AL 2,551,672

HIGH-FREQUENCY ELECTRICAL RESONATOR Filed Jan. 22, 1947 2 Sheets-Sheet l I I ZSnnentors Awzazz .5. Harris & Qala nd F Prado/ y 3951 N. L. HARRIS ET AL 2,551,672

HIGH-FREQUENCY ELECTRICAL RESONATOR Filed Jan. 22, 1947 2 Sheets-Sheet 2 fl mw Z1 $7 2 2? 5foiaw a F Prado) Patented May 8, 1951 2,551,672 HIGH-FREQUENCY crccrmoac RESONATOR Norman L. Harris, Batch End, and Roland F. Proctor, Christchurch, England, assignors to M. 0. Valve Company Limited, a corporation of Great Britain Application January 22, 1947, Serial No. 723,552 In Great Britain October 8, 1940 Section 1, Public Law 690, August 8, 1946 Patent expires October 8, 1960 This invention relates to high frequency electrical resonators and more particularly to cavity resonators of the torroidal type.

The invention is particularly directed to means for adjusting the effective size of the cavity and thereby controlling the natural resonant frequency of the resonator.

An object of the invention is to provide a compact and solid resonator structure which can easily be adjusted in effective size within practical limits.

Another object of the invention is to provide a resonator which may have an evacuated portion and be adjustable as to resonance without disturbing the existing vacuum.

An advantage of the invention is that adjustment of the resonator may be effected by simple means and under actual operating conditions.

Other objects and advantages will be apparent from the following description of the invention, pointed out in particularity in the appended claims and taken in connection with the accompanying drawing, in which:

Fig. 1 is a sectional view partly in perspective of a resonator in accordance with the invention and representing a section taken along line |l of Fig. 2.

Fig. 2 is a top view with a cutaway portion along line 22 of Fig. 1.

Fig. 3 is a top View of a modified form partly in section taken along line 3-3 of Fig. 4.

Fig. 4 is a sectional view partly in perspective taken along line 45 of Fig. 3.

It is to be noted that in the above illustrations the invention is applied to the type of resonators in which an evacuated space is a part of the total space enclosed by the boundary walls of the resonator. While the invention is particularly useful in connection with these types, it is not limited thereto and may be applied to various types of cylindrical resonators. Essentially the invention in its broader aspect comprises a resonant cavity which is bounded by a pair of parallel walls and a tubular wall which is perpendicular to the parallel walls. The perimeter and eiTective diameter of the tubular wall is adjustable whereby the size 11 Claims. (01. 178-44) of the cavity and consequently the resonance of H bounded on the side by a concentric flexible band 5 perpendicular to the plates 3 and 4.

The cavity so formed is divided by the tubular member I which is of insulating material transparent to electromagnetic radiation such as glass or ceramic and extends outwardly coaxially from both plates 3 and 4 and also continues therebetween. The continuation of the tubular member 1 between the plates identified by reference character 8 forms a ring between the plates which is sealed at the junction so that a portion of the cavity lying within the range 8 is hermetically sealed from the rest. This portion may be evacuated through the tube 1. The wall of the ring 8 need not be aligned with the wall of the tubular member I as shown. This construction is merely convenient in manufacture.

As stated before, the side of the resonator consists of a flexible band 5 which, as seen in Fig. 2. is provided with a number of reinforcing ribs 9 across it. These ribs allow an increased area of contact between the band 5 and the plates 3 and. i and are sufficiently separated so that the flexibility of the band 5 is not materially decreased. As can be seen, the band 5 is overlapping. Its diameter therefore may be made longer or smaller within limits depending upon the extent of the overlap. For a fine adjustment of the band and thereby for the change in the efiective size and natural frequency of the cavity, there is shown by way of example a micrometer type screw 10 hinged at a suitable point to the band 5 and running into an eyelet H aiiixed to the other end of the band 5. A nut l2 on the screw H] cooperates with the eyelet H and thereby the circumference and effective diameter of the band 5 may be adjusted. Of course various other means may equally be employed for contracting or expaneling the band 5.

In order to have a solid and rigid structure, a number of clamps l4 held by bolts I5 are distributed around the resonator and serve to press the plates 3 and 4 against the edge of the band 5. When adjustment of the cavity is desired, the bolts 55 are sufliciently loosened to release the clamps H! and allow free movement of the band 5. After the latter is compressed or expanded, as the case may be, the assembly is bolted down-tight by means of the clamps [3.

It is to be noted that the effective cavity size of the resonator which includes both the portions outside and inside the dividing ring 8 may be changed without interfering with the evacuated space. This is particularly advantageous in these types of resonators because the tubular member 1 usually terminates at one end in an' electronemitting cathode and at the other end in a collooting, electrode The vacuum in such an assembly must be maintained and cannot be altered during operation. Needless to say the adjustable feature shown is equally applicable to plain resonators without the evacuable portion.

The modification shown in Figs. 3 and 4 provides a rigid side wall for the resonator instead of the flexible one described. Two semi-circular forked members l1 and H, one overlapping the other, are clamped between the plates 3 and 4. Each of the forked members is slidable with respect to the other so that the extent of overlap may be adjusted and thereby effective diameter of the space bounded by the members I! and I1 may be changed. This obviously changes effective size of the resonator cavity.

The plates 3 and 4 are clamped together by clamps l8 peripherally distributed and so dimensioned as to keep the plates 3 and 4 in close contact with the forked members I! and [1 although permitting the sliding of these members for adjustment. A simple adjusting means is provided by the screws 20 and 20 which are threaded in oppositely placed clamps l8 and are rotatably attached to forked members IT and I1, respectively. By the adjustment of these screws, both members I! and I1 may be slidably adjusted with respect to their overlap and also with respect to the evacuable portion separated by the ring 8.

We claim: 1. A cavity resonator comprising a pair of end plate members, means rigidly positioning said plate members in predetermined spaced parallel relation, a tubular side wall independent of said means extending between and slidably engaging said end plate members at points spaced inwardly from the outer extremities thereof, and additional vmeans rigidly positioned with respect to said positioning means and said plate members for sliding said side wall inwardly and outwardly along said end plate members to change the volume and resonant frequency of said resonator axially from both said plate members and continuing between said members outside said aperture and dividing said resonator into an evacuable portion and a portion non-evacuable, said tubular member circumferentially enclosing said aperture, a flexible band surrounding and concentric with said tubular member and perpendicular to the inner surfaces of said flat portions and forming the side wall of said resonator, said band being adjustable in circumference, and clamping means securing said plate members to said side.

3. An electric resonator in accordance with claim 2, wherein said flexible band has a plurality of axially disposed reinforcing ribs perpendicular to the inner surfaces of said flat portions.

4. An electric resonator in accordance with claim 3 in which said flexible band overlaps and has at one end an eyelet and near the other end a hinged screw adapted to fit into said eyelet and a nut on said screw cooperating with said eyelet for controlling the extent of overlapping of said band.

5. An electric resonator of the cavity type comprising a pair of juxtaposed parallel plate members each having a flat portion and an inwardly curved portion in the center, said inwardly curved portions of said plate members forming a central aperture and being spaced apart forming an annular gap in said resonator, a pair of oppositely placed overlapping semi-circular forked members one of which is slidable into the other extending between said fiat portions, said forked members forming the side wall of said resonator and determining the enclosed cavity, clamping means disposed around said plate members and engaging the outer surface thereof, and adjusting means for sliding said forked members thereby controlling the relative overlapping of said forked members.

6. An electric resonator in accordance with claim 5 in which said adjusting means comprises a screw attached to each of said forked members and each threaded in said clamping means.

'7. A cavity resonator comprising a pair of parallel walls and a tubular wall extending between said parallel walls and having at least a portion thereof slidably engaging said parallel walls at points spaced inwardly from the outer extremities thereof, said parallel walls and tubular wall enclosing a cavity, a rigid tubular member of a material transparent to electromagnetic radiation sealed to said parallel walls within said tubular wall and dividing said cavity into an inner evacuable portion and an outer non-evacuable portion, and means for sliding said tubular wall portion toward and away from said tubular member, whereby the effective size and resonant frequency of said resonator may be altered without disturbing said evacuable portion.

8. A cavity resonator according to claim 7, wherein said tubular wall comprises a flexible band, and said means comprises means for adjusting the circumference of said band.

9. An electric resonator in accordance with claim 5, further including a rigid tubular member of a material transparent to electromagnetic radiation sealed to said plate members between said aperture and said resonator side wall and dividing said resonator into an inner evacuable portion and an outer non-evacuable portion.

10. A cavity resonator comprising a pair of a parallel conducting walls, a tubular side wall comprising a pair of oppositely-disposed relatively-slidable semi-circular conducting wall members extending between and slidably engaging said parallel walls, and adjusting means for relatively sliding said semi-circular wall members to change the siz of said resonator.

11. A cavity resonator in accordance with claim 10, further including a rigid tubular member of a material transparent to electromagnetic radiation sealed to said parallel walls within said tubular side wall and dividing said resonator into an inner evacuable portion and an outer nonevacuable portion.

NORMAN L. HARRIS. R. F. PROCTOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,044,413 Weyrich June 16, 1986 2,253,589 Southworth Aug. 26, 1941 2,406,370 Hanson Aug. 27, 1946 2,410,109 Schelling Oct. 29, 1946 

